Electronic structure nitrous oxide

It is analogous to the fourth structure for carbon dioxide, which has the same number of electrons as nitrous oxide, and might be of importance for the latter molecule also. Resonance among the four structures, contributing equally, leads to the values N—N = 1.15AandN—0 = 1.11 A that is, to an N—O distance smaller than the N—N distance, which is contrary to observation 18 N—N = 1.126 A, N—N = 1.186 A. The observed values are those expected for resonance among the first three structures. 

Nitrous oxide is a moderately unreactive gas comprised of linear unsymmetrical molecules, as expected for a 16-electron triatomic species (p. 433). The symmetrical structure N-O-N is precluded on the basis of orbital energetics. Some physical properties are in Table 11.8 it will be seen that the N-N and N-O distances are... 

Nitric oxide is the simplest thermally stable odd-electron molecule known and, accordingly, its electronic structure and reaction chemistry have been very extensively studied. The compound is an intermediate in the production of nitric acid and is prepared industrially by the catalytic oxidation of ammonia (p. 466). On the laboratory scale it can be synthesized from aqueous solution by the mild reduction of acidified nitrites with iodide or ferrocyanide or by the disproportionation of nitrous acid in the presence of dilute sulfuric acid ... 

The investigation of methyl azide, methyl nitrate, and fluorine nitrate by electron diffraction is shown to lead to configurations of the molecules corresponding in each case to resonance between two important valence-bond structures. The unimportance of a third otherwise reasonable structure for these molecules as well as for nitrous oxide is ascribed to instability due to the presence of electric charges of the same sign on adjacent atoms. It is shown that the differ-... 

The oxides of nitrogen that have been well characterized are described in Table 14.4. Nitrous oxide (m.p. -91 °C, b.p. -88 °C) is a 16-electron triatomic molecule having a linear structure. Three resonance structures can be drawn for this molecule as follows ... 

The decomposition of nitrous oxide over various metal oxides has been widely investigated by many investigators (1-3). Dell, Stone and Tiley (4) have compared the reactivity of metal oxides and shown that in general p-type oxides were the best catalysts and n-type the worst, with insulators occupying an intermediate position. It has been generally accepted (5) that this correlation indicates that the electronic structure of the catalyst is an important factor in the mechanism of the decomposition of nitrous oxide over metal oxides catalysts. The reaction is usually written (4) as... 

Nitrous oxide (N2O, see Section 2.11) is a colorless, odorless gas with mildly anaesthetic properties (laughing gas). It is formed in Nature by bacterial reduction of nitrates. The electronic structure of this linear molecule is best understood by noting that it is isoelectronic with CO2, which is also linear. It is rather easily decomposed into N2 and 02, and so can support combustion. 

The discussion in Section 1-3 about the element of arbitrariness in the concept of resonance may be recalled at this point with reference to the nitrous oxide molecule and the other molecules that are described in this chapter as resonating among several valence-bond structures. It is not necessary that the structures A, B, and C be used as the basis of discussion of the nitrous oxide molecule. We might say instead that the molecule cannot be satisfactorily represented by any single valence-bond structure, and abandon the effort to correlate its structure and properties with those of other molecules. By using valence-bond structures as the basis for discussion, howrever, with the aid of the concept of resonance, we are able to account for the properties of the molecule in terms of those of other molecules in a straightforward and simple way. It is for this practical reason that we find it convenient to speak of the resonance of molecules among several electronic structures. 

PROBLEM 7.12 Called "laughing gas," nitrous oxide (N2O) is sometimes used by dentists as an anesthetic. Given the connections N-N-0 draw two electron-dot resonance structures for N2O. 

A. 0. Rankine found that the mols. of nitrous oxide and carbon dioxide behave physically as if they had the same size, shape, and electronic structure. I. Langmuir compared the physical properties of carbon dioxide and of nitrous oxide, and the similarity was attributed to a like electronic structure—vide 4. 27, 4, Fig. 30. G. Kirsch made observations on the electronic structure of the molecule and M. L. Huggins made estimates of the interatomic distances. 

The dehydration of the syn-form of hyponitrous acid is supposed by A. Hantzsch to furnish nitrous oxide. H. Henstock gave for the electronic structure ... 

As the focus of this review is on copper-dioxygen chemistry, we shall briefly summarize major aspects of the active site chemistry of those proteins involved in 02 processing. The active site structure and chemistry of hemocyanin (He, 02 carrier) and tyrosinase (Tyr, monooxygenase) will be emphasized, since the chemical studies described herein are most relevant to their function. The major classes of these proteins and their origins, primary functions, and leading references are provided in Table 1. Other classes of copper proteins not included here are blue electron carriers [13], copper-thiolate proteins (metallothioneines) [17], and NO reductases (e.g., nitrite [NIR] [18] or nitrous oxide [19]). 

Example Which of the electron-dot structures given below for nitrous oxide (laughing gas), N2O, is/are acceptable ... 

Nitrous oxide, N20 16 valence electrons. Here, two skeletons come to mind, NNO and NON. The structure NNO is suggested by chemical evidence and confirmed by spectral studies (Chap. 25). There are three distributions of electrons consistent with the octet rule ... 

For many simple compounds having no more than one double bond, the modern picture may be quite adequately represented by the Lewis structures (although the Lewis rules are noncommittal about the shapes of molecules). For compounds such as butadiene, benzene, and nitrous oxide, where there is extensive delocalization of electron density, the Lewis structures are not as suitable as the x-electron structures or, better still, as the streamer structures. Both of the latter type, however, are more difficult to draw and, for more complex molecules, more difficult to visualize they become extremely unwieldy when one attempts to use them to represent the progress of a chemical reaction. 

Nitrous oxide, nitric oxide, nitrogen trioxide, nitrogen dioxide, dinitrogen te-troxide, nitrogen pentoxide their properties, method of formation, and electronic structure. 

Another approach to the relationship between electronic structure and catalysis has been the search for catalytic activity patterns based on electron configuration and semiconductor type. The first of these patterns to be established was in nitrous oxide decomposition (69-71), as illustrated in Fig. 8. This series, with one or two exceptions, divides remarkably into... 

In basic solutions ascorbate is apparently oxidized preferentially by the electron transfer process, which goes to completion in less than 2 fts after termination of the electron pulse (see Structure I). In nitrous-oxide-saturated acid solutions (pH 3.0-4.5), A and two other species which were shown to be OH-radical adducts were observed (37), thus confirming earlier observations (18,19,23, 25). The ascorbate radical anion was identified by its doublet of triplets spectrum that maintains its line position from pH 13 to 1. One OH-radical adduct (IV) shows a doublet, the lines of which start to shift below pH 3.0 it has a pK near 2.0, a decay period of about 100 fxs, and probably does not lead to formation of A". The other OH-radical adduct (II) is formed by addition of the OH radical to the C2 position its ESR parameters are = 24.4 0.0002 G and g == 2.0031 0.0002. Time growth studies suggest that this radical adduct converts to the ascorbate anion radical (III) with r 15 fxs, and accounts for 50% of the A signal intensity 40 fxS after termination of the electron pulse. The formation of the three radicals can be summarized as shown in Scheme 1. 

Fujiwara and Fukumori, 1996). Nitric oxide reductase is also known, which lacks heme C and uses quinol as the electron donor (Suharti et al., 2001 de Vries et al., 2003). The cytochrome ebb-type enzyme has a molecular structure similar to the structure of the Cub binding portion in cytochrome c oxidase (Saraste and Castresana, 1994 Van der Oost et al., 1994 Zumft et al., 1994). Moreover, quinol NO reductase from Bacillus azotoformans is known to contain Cua. Nitrous oxide is further reduced to nitrogen gas (N2) by the catalysis of nitrous oxide reductase (N20 reductase) which is a multi-copper protein (Zumft and Matsubara, 1982). The structure of the copper-binding portion in the enzyme has been reported also to be similar to the structure of the Cua binding portion of cytochrome c oxidase (Chamock et al., 2000). 

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